preamp tube hiss from my SF Line 1

I'm trying to diagnose a very audible hissing sound that recently showed up. The symptoms are, hissing sound coming from the right speaker. Its very noticable from my chair. It does not get louder as I turn up the volume. The sound is there regardless of which input I select. It does go away when I switch on the HT Passthrough. I thought I had a bad tube and have tried swapping out each of the three tubes ont the right channel and it makes no difference. All the tubes are NOS Amperex and I've been using them for a while now without any issue. This all started when I swapped out the bottom pair of tubes with some better ones that I had. All my tubes were recently tested so I know they still have plenty of life in them. Any ideas? I find it unlikely that I have multiple noisy tubes, but of course I could try putting the stock ones in all three right positions. Any insight would be appriciated.
I can't determine from your post if you tried swapping the left channel tubes with those of the right channel. If the hissing changes from the right speaker to the left speaker, you now know that you have a bad tube. Once you have established that you have a bad tube in one channel, switch out one tube at a time from right to left channel until you notice that the hissing has also changed from the associated channel. It is merely a process of elimination. Good luck.
Just grabbing at straws here, but is there a chance you may have a cold solder joint on one of the tube socket terminals caused when changing out the tubes? If you put back in the three tubes you had pulled before the hiss, and you still have it, then I think that eliminates the tubes from the equations.
Snipes, I have owned a Sonic Frontiers preamp before with the same problem but my hiss was in the left channel. Called SF and they told me that the Mosfet transistor that followed the tube had become noisy & if I could tolerate the hiss it was not necessary to replace. To cure this hiss of course is to replace the Mosfet follower.

Another thing to keep in mind as when you swap out tubes it is important to wait at least two minutes after turning the unit off before doing so otherwise damaged can occur to the Mosfet follower. I am assuming the SF Line 1 is a hybrid like the SFL-1 which I had owned. Hope this helps.
Brf: I swapped out one tube at a time using an extra tube I had. I've actually tried a few "extra" tubes, swapping out only one a time and get the same result. My next step is to put all six stock tubes in it and see what happens.

Jea48: You wrote: "If you put back in the three tubes you had pulled before the hiss, and you still have it, then I think that eliminates the tubes from the equations." I'm not following you. If I put the same tubes back in and the hiss is still there I don't see how I ruled out the tubes. If it is a bad tube, then wouldn't putting it back in cause the hiss to continue? The hissing didn't start until after I swapped out a pair of tubes. Maybe I did in fact break a solder joint. There aren't any error lights on though..

Phd: Did you happen to get an estimate on the repair work? The hiss is very audible and I won't be able to live w/it. Thanks for the info.

Thanks for all the suggestions. I'll update the thread after I swap out all six. I've had good luck with SF / Anthem tech support so I think it's time to shoot them an email as well.
One more piece of information. The hissing doesn't start until about 1 minute after the input is anything other than SSP. Assuming the starting point was the SSP or coming out of standby. This happened every time after I swapped out a tube trying to diagnose the issue earlier in the week. The previous instances were after powering the pre, this time the same thing happened after switching the source from SSP(HT passthrough) to the CD player. The pre has been running for a few hours so it's nice a warmed up. It seems more and more relevant considering it's a consistant issue after about a minute.
Snipes, I did get an estimate from SF but that was last year & can't remember the exact dollar figure but it wasn't alot. In my case as well, sometimes the hiss was not there when it was initially turned on but became evident as the unit was left powered up.

With hybrids tube rolling can be fun but you always have to make sure the unit has been powered off at least two minutes before swapping tubes, (100% tube designs being the exception). My belief that this is the leading cause of failure to the solid state followers. Some mfgs will stress this in the manual. Unfortunately not all of us are aware of this problem as some units are purchased without the manual or the manual is not read thoroughly.

Jea48 mentioned another good point with cold solder joints & could be looked into as well.
Unfortunately, a lot of parts in SFequipment went bad. I don't know why, since they used lots of quality components. Perhaps it was the circuit design. As much as I loved the SF stuff, so gorgeous and heavy, this is the reason I don't and won't own any of their gear, especially since they are out of business. I find it amazing how many people buy the used preamps and amps. This is what you have to look forward to.
>>"Jea48: You wrote: "If you put back in the three tubes you had pulled before the hiss, and you still have it, then I think that eliminates the tubes from the equations." I'm not following you. If I put the same tubes back in and the hiss is still there I don't see how I ruled out the tubes. If it is a bad tube, then wouldn't putting it back in cause the hiss to continue?"<<
I misunderstood the start of your thread. I thought you had reinstalled the original tubes, the tubes that were in the Line One before the hiss problem.

If the preamp did not hiss before you pulled the original tubes, but did after installing the NOS tubes, then I suggest you start from ground zero. Pull all of the 6 nos tubes and reinstall the original 6 tubes. Make sure you keep the right channel tubes separated from the left channel tubes when you pull them. If the hiss is not there, then that's great news.... That means that one, or more, of the nos tubes you pulled from the right channel is either shorted or has excessive grid emissions.

Post back after you install the original tubes.......good luck.

Phd, the Sonic Frontiers Line one, two , and three, are not hybrids as far as I know. The SFL-1 is a hybrid.

Snipes, curiosity killed the cat!!
How about an update.....
Snipes, I agree with Jea48, let us know!
I've been tied up this week. Plan to swap out all the tubes in the next day or two. I'll update the thread with my findings.
No update yet. Hope to get to it this week.
I finally got around to working out the problem today. SUCCESS!! The problem was due to noisy tubes. I had one very noisy tube and one of my spare tubes of the same type, Amperex Jan Green, was also very noisy. Luckily I had a few more good spares and was eventually able to find 6 tubes that were dead quite. Funny thing is I ended up with the same setup I was running before all of this business started up. Amperex Jan Greens up top, Amperex USA Whites in the middle and a pair of Russian Rockets (not sure what they are) in the bottom pair. It was the bottom pair I tried swapping out when all of this started up. I put my Herbie tube dampers back on and I'm back in business.
Thanks to everyone for their interest and help.
Snipes that's excellent! Keep playing them tunes!
Snipes, sounds great. Glad to hear you are back in business.

Just to clarify your tube placement in order of importance.

(1) Middle row, LV2 -- V2
(2) Back row, LV1 -- V1
(3) Front row, LV3 -- V3

Where do you have the Herbies HAL O dampers positioned?
I run mine near the top of the tubes.
Jea48: I remember one of your previous threads concerning the order of importance and yes, that's how I have them. I run the tube dampers about 25% the way down from the top. I didn't play around with placement much as the concensus seems to be towards the top like you mention. Any experience or have you heard comments concerning some of the new EH gold pin tubes in the SF line? I'm curious about how they might sound. At $15 a pop for brand new tubes, it's tempting. I've read that their production quality has really been improving, whatever that means.

Snipes, just buy two matched pairs of the EH tubes and try them. Be careful who you buy them from. Quality control in Russia ain't the best. A good dealer will throw away tubes that don't meet their specs. Some will pass marginal tubes and sell them to customers anyway.

If you do not like the sound you can move one pair to the front row LV3 -- V3. Put the other pair back in the boxes for backup and future.

If you do go for it post back and lets us know how they sound.
I just experienced a static/hiss last night for the first time. Kind of like when a turntable reaches the end of a record. Not noticeable during music, but noticeable when I hit 'pause'. I swapped cables on the amps and source, and isolated it to one side of my preamp (BAT VK30, with 6 6H23 Russian Rocket logos, 2.5 years old). Later that evening, the noise mostly went away. So, I was wondering . . .

-should I isolate the one bad tube and replace it?
-or, should I replace a pair of tubes to keep the same age on them?
-just wait for the noise to come back?
-is this noise a warning that the tube will have a catastrophic failure in the near future?

thanks for your help and advice
My problem turned out to be two seperate tubes were making noise. It took a while to troubleshoot, luckily I had a nice stash of extra tubes to mix and match while trying to isolate it. I'd just replace the problem tube unless they are inexpensive and you think they are getting up there in age.
Thanks for you reply, Snipes.

In my case the problem came on suddenly, so I would think it would be one tube vs. two. Do you think 2.5 years is 'getting up there in age?' I probably do 5 hrs per week, so maybe 700 hrs at this point?